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                    程序结构
            
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                    变量
            
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                    赋值
            
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                    类型
            
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                    包和文件
            
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                    作用域
            
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                    基础数据类型
            
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                    整型
            
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                    浮点数
            
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                    布尔型
            
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                    字符串
            
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                    常量
            
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                    复合数据类型
            
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                    数组
            
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                    Slice
            
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                    Map
            
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                    结构体
            
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                    JSON
            
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                    文本和HTML模板
            
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                    函数
            
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                    函数声明
            
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                    递归
            
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                    多返回值
            
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                    错误
            
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                    函数值
            
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                    匿名函数
            
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                    可变参数
            
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                    Deferred函数
            
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                    Panic异常
            
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                    Recover捕获异常
            
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                    方法
            
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                    方法声明
            
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                    基于指针对象的方法
            
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                    通过嵌入结构体来扩展类型
            
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                    方法值和方法表达式
            
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                    示例: Bit数组
            
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                    封装
            
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                    接口
            
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                    接口是合约
            
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        <li class="chapter " data-level="1.8.2" data-path="../ch7/ch7-02.html">
            
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                    接口类型
            
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        <li class="chapter " data-level="1.8.3" data-path="../ch7/ch7-03.html">
            
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                    实现接口的条件
            
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        <li class="chapter " data-level="1.8.4" data-path="../ch7/ch7-04.html">
            
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                    flag.Value接口
            
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        <li class="chapter " data-level="1.8.5" data-path="../ch7/ch7-05.html">
            
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                    接口值
            
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        <li class="chapter " data-level="1.8.6" data-path="../ch7/ch7-06.html">
            
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                    sort.Interface接口
            
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        <li class="chapter " data-level="1.8.7" data-path="../ch7/ch7-07.html">
            
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                    http.Handler接口
            
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        <li class="chapter " data-level="1.8.8" data-path="../ch7/ch7-08.html">
            
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                    error接口
            
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                    示例: 表达式求值
            
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        <li class="chapter " data-level="1.8.10" data-path="../ch7/ch7-10.html">
            
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                    类型断言
            
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        <li class="chapter " data-level="1.8.11" data-path="../ch7/ch7-11.html">
            
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                    基于类型断言识别错误类型
            
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        <li class="chapter " data-level="1.8.12" data-path="../ch7/ch7-12.html">
            
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                    通过类型断言查询接口
            
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        <li class="chapter " data-level="1.8.13" data-path="../ch7/ch7-13.html">
            
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                    类型分支
            
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        <li class="chapter " data-level="1.8.14" data-path="../ch7/ch7-14.html">
            
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                    示例: 基于标记的XML解码
            
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                    补充几点
            
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        <li class="chapter " data-level="1.9" data-path="../ch8/ch8.html">
            
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                    Goroutines和Channels
            
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                    Goroutines
            
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        <li class="chapter " data-level="1.9.2" data-path="../ch8/ch8-02.html">
            
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                    示例: 并发的Clock服务
            
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        <li class="chapter " data-level="1.9.3" data-path="../ch8/ch8-03.html">
            
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                    示例: 并发的Echo服务
            
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        <li class="chapter " data-level="1.9.4" data-path="../ch8/ch8-04.html">
            
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                    Channels
            
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        <li class="chapter " data-level="1.9.5" data-path="../ch8/ch8-05.html">
            
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                    并发的循环
            
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        <li class="chapter " data-level="1.9.6" data-path="../ch8/ch8-06.html">
            
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                    示例: 并发的Web爬虫
            
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        <li class="chapter " data-level="1.9.7" data-path="../ch8/ch8-07.html">
            
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                    基于select的多路复用
            
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        <li class="chapter " data-level="1.9.8" data-path="../ch8/ch8-08.html">
            
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                    示例: 并发的目录遍历
            
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        <li class="chapter " data-level="1.9.9" data-path="../ch8/ch8-09.html">
            
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                    并发的退出
            
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        <li class="chapter " data-level="1.9.10" data-path="../ch8/ch8-10.html">
            
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                    示例: 聊天服务
            
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        <li class="chapter " data-level="1.10" data-path="../ch9/ch9.html">
            
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                    基于共享变量的并发
            
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                    竞争条件
            
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        <li class="chapter " data-level="1.10.2" data-path="../ch9/ch9-02.html">
            
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                    sync.Mutex互斥锁
            
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        <li class="chapter " data-level="1.10.3" data-path="../ch9/ch9-03.html">
            
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                    sync.RWMutex读写锁
            
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        <li class="chapter " data-level="1.10.4" data-path="../ch9/ch9-04.html">
            
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                    内存同步
            
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        <li class="chapter " data-level="1.10.5" data-path="../ch9/ch9-05.html">
            
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                    sync.Once惰性初始化
            
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        <li class="chapter " data-level="1.10.6" data-path="../ch9/ch9-06.html">
            
                <a href="../ch9/ch9-06.html">
            
                    
                    竞争条件检测
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.10.7" data-path="../ch9/ch9-07.html">
            
                <a href="../ch9/ch9-07.html">
            
                    
                    示例: 并发的非阻塞缓存
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.10.8" data-path="../ch9/ch9-08.html">
            
                <a href="../ch9/ch9-08.html">
            
                    
                    Goroutines和线程
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.11" data-path="../ch10/ch10.html">
            
                <a href="../ch10/ch10.html">
            
                    
                    包和工具
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.11.1" data-path="../ch10/ch10-01.html">
            
                <a href="../ch10/ch10-01.html">
            
                    
                    包简介
            
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                    导入路径
            
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                    包声明
            
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        <li class="chapter " data-level="1.11.4" data-path="../ch10/ch10-04.html">
            
                <a href="../ch10/ch10-04.html">
            
                    
                    导入声明
            
                </a>
            

            
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        <li class="chapter " data-level="1.11.5" data-path="../ch10/ch10-05.html">
            
                <a href="../ch10/ch10-05.html">
            
                    
                    包的匿名导入
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.6" data-path="../ch10/ch10-06.html">
            
                <a href="../ch10/ch10-06.html">
            
                    
                    包和命名
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.7" data-path="../ch10/ch10-07.html">
            
                <a href="../ch10/ch10-07.html">
            
                    
                    工具
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.12" data-path="../ch11/ch11.html">
            
                <a href="../ch11/ch11.html">
            
                    
                    测试
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.12.1" data-path="../ch11/ch11-01.html">
            
                <a href="../ch11/ch11-01.html">
            
                    
                    go test
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.12.2" data-path="../ch11/ch11-02.html">
            
                <a href="../ch11/ch11-02.html">
            
                    
                    测试函数
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.12.3" data-path="../ch11/ch11-03.html">
            
                <a href="../ch11/ch11-03.html">
            
                    
                    测试覆盖率
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.12.4" data-path="../ch11/ch11-04.html">
            
                <a href="../ch11/ch11-04.html">
            
                    
                    基准测试
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.12.5" data-path="../ch11/ch11-05.html">
            
                <a href="../ch11/ch11-05.html">
            
                    
                    剖析
            
                </a>
            

            
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        <li class="chapter " data-level="1.12.6" data-path="../ch11/ch11-06.html">
            
                <a href="../ch11/ch11-06.html">
            
                    
                    示例函数
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.13" data-path="../ch12/ch12.html">
            
                <a href="../ch12/ch12.html">
            
                    
                    反射
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.13.1" data-path="../ch12/ch12-01.html">
            
                <a href="../ch12/ch12-01.html">
            
                    
                    为何需要反射?
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.13.2" data-path="../ch12/ch12-02.html">
            
                <a href="../ch12/ch12-02.html">
            
                    
                    reflect.Type和reflect.Value
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.13.3" data-path="../ch12/ch12-03.html">
            
                <a href="../ch12/ch12-03.html">
            
                    
                    Display递归打印
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.13.4" data-path="../ch12/ch12-04.html">
            
                <a href="../ch12/ch12-04.html">
            
                    
                    示例: 编码S表达式
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.13.5" data-path="../ch12/ch12-05.html">
            
                <a href="../ch12/ch12-05.html">
            
                    
                    通过reflect.Value修改值
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.13.6" data-path="../ch12/ch12-06.html">
            
                <a href="../ch12/ch12-06.html">
            
                    
                    示例: 解码S表达式
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.13.7" data-path="../ch12/ch12-07.html">
            
                <a href="../ch12/ch12-07.html">
            
                    
                    获取结构体字段标签
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.13.8" data-path="../ch12/ch12-08.html">
            
                <a href="../ch12/ch12-08.html">
            
                    
                    显示一个类型的方法集
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.13.9" data-path="../ch12/ch12-09.html">
            
                <a href="../ch12/ch12-09.html">
            
                    
                    几点忠告
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.14" data-path="../ch13/ch13.html">
            
                <a href="../ch13/ch13.html">
            
                    
                    底层编程
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.14.1" data-path="../ch13/ch13-01.html">
            
                <a href="../ch13/ch13-01.html">
            
                    
                    unsafe.Sizeof, Alignof 和 Offsetof
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.14.2" data-path="../ch13/ch13-02.html">
            
                <a href="../ch13/ch13-02.html">
            
                    
                    unsafe.Pointer
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.14.3" data-path="../ch13/ch13-03.html">
            
                <a href="../ch13/ch13-03.html">
            
                    
                    示例: 深度相等判断
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.14.4" data-path="../ch13/ch13-04.html">
            
                <a href="../ch13/ch13-04.html">
            
                    
                    通过cgo调用C代码
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.14.5" data-path="../ch13/ch13-05.html">
            
                <a href="../ch13/ch13-05.html">
            
                    
                    几点忠告
            
                </a>
            

            
        </li>
    

            </ul>
            
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        <li class="chapter " data-level="1.15" data-path="../appendix/appendix.html">
            
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                    附录
            
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            <ul class="articles">
                
    
        <li class="chapter " data-level="1.15.1" data-path="../appendix/appendix-a-errata.html">
            
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                    附录A：原文勘误
            
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                    附录B：作者译者
            
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                    附录C：译文授权
            
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                    附录D：其它语言
            
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    <h1>
        <i class="fa fa-circle-o-notch fa-spin"></i>
        <a href=".." >Map</a>
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                                <h2 id="43-map">4.3. Map</h2>
<p>&#x54C8;&#x5E0C;&#x8868;&#x662F;&#x4E00;&#x79CD;&#x5DE7;&#x5999;&#x5E76;&#x4E14;&#x5B9E;&#x7528;&#x7684;&#x6570;&#x636E;&#x7ED3;&#x6784;&#x3002;&#x5B83;&#x662F;&#x4E00;&#x4E2A;&#x65E0;&#x5E8F;&#x7684;key/value&#x5BF9;&#x7684;&#x96C6;&#x5408;&#xFF0C;&#x5176;&#x4E2D;&#x6240;&#x6709;&#x7684;key&#x90FD;&#x662F;&#x4E0D;&#x540C;&#x7684;&#xFF0C;&#x7136;&#x540E;&#x901A;&#x8FC7;&#x7ED9;&#x5B9A;&#x7684;key&#x53EF;&#x4EE5;&#x5728;&#x5E38;&#x6570;&#x65F6;&#x95F4;&#x590D;&#x6742;&#x5EA6;&#x5185;&#x68C0;&#x7D22;&#x3001;&#x66F4;&#x65B0;&#x6216;&#x5220;&#x9664;&#x5BF9;&#x5E94;&#x7684;value&#x3002;</p>
<p>&#x5728;Go&#x8BED;&#x8A00;&#x4E2D;&#xFF0C;&#x4E00;&#x4E2A;map&#x5C31;&#x662F;&#x4E00;&#x4E2A;&#x54C8;&#x5E0C;&#x8868;&#x7684;&#x5F15;&#x7528;&#xFF0C;map&#x7C7B;&#x578B;&#x53EF;&#x4EE5;&#x5199;&#x4E3A;map[K]V&#xFF0C;&#x5176;&#x4E2D;K&#x548C;V&#x5206;&#x522B;&#x5BF9;&#x5E94;key&#x548C;value&#x3002;map&#x4E2D;&#x6240;&#x6709;&#x7684;key&#x90FD;&#x6709;&#x76F8;&#x540C;&#x7684;&#x7C7B;&#x578B;&#xFF0C;&#x6240;&#x6709;&#x7684;value&#x4E5F;&#x6709;&#x7740;&#x76F8;&#x540C;&#x7684;&#x7C7B;&#x578B;&#xFF0C;&#x4F46;&#x662F;key&#x548C;value&#x4E4B;&#x95F4;&#x53EF;&#x4EE5;&#x662F;&#x4E0D;&#x540C;&#x7684;&#x6570;&#x636E;&#x7C7B;&#x578B;&#x3002;&#x5176;&#x4E2D;K&#x5BF9;&#x5E94;&#x7684;key&#x5FC5;&#x987B;&#x662F;&#x652F;&#x6301;==&#x6BD4;&#x8F83;&#x8FD0;&#x7B97;&#x7B26;&#x7684;&#x6570;&#x636E;&#x7C7B;&#x578B;&#xFF0C;&#x6240;&#x4EE5;map&#x53EF;&#x4EE5;&#x901A;&#x8FC7;&#x6D4B;&#x8BD5;key&#x662F;&#x5426;&#x76F8;&#x7B49;&#x6765;&#x5224;&#x65AD;&#x662F;&#x5426;&#x5DF2;&#x7ECF;&#x5B58;&#x5728;&#x3002;&#x867D;&#x7136;&#x6D6E;&#x70B9;&#x6570;&#x7C7B;&#x578B;&#x4E5F;&#x662F;&#x652F;&#x6301;&#x76F8;&#x7B49;&#x8FD0;&#x7B97;&#x7B26;&#x6BD4;&#x8F83;&#x7684;&#xFF0C;&#x4F46;&#x662F;&#x5C06;&#x6D6E;&#x70B9;&#x6570;&#x7528;&#x505A;key&#x7C7B;&#x578B;&#x5219;&#x662F;&#x4E00;&#x4E2A;&#x574F;&#x7684;&#x60F3;&#x6CD5;&#xFF0C;&#x6B63;&#x5982;&#x7B2C;&#x4E09;&#x7AE0;&#x63D0;&#x5230;&#x7684;&#xFF0C;&#x6700;&#x574F;&#x7684;&#x60C5;&#x51B5;&#x662F;&#x53EF;&#x80FD;&#x51FA;&#x73B0;&#x7684;NaN&#x548C;&#x4EFB;&#x4F55;&#x6D6E;&#x70B9;&#x6570;&#x90FD;&#x4E0D;&#x76F8;&#x7B49;&#x3002;&#x5BF9;&#x4E8E;V&#x5BF9;&#x5E94;&#x7684;value&#x6570;&#x636E;&#x7C7B;&#x578B;&#x5219;&#x6CA1;&#x6709;&#x4EFB;&#x4F55;&#x7684;&#x9650;&#x5236;&#x3002;</p>
<p>&#x5185;&#x7F6E;&#x7684;make&#x51FD;&#x6570;&#x53EF;&#x4EE5;&#x521B;&#x5EFA;&#x4E00;&#x4E2A;map&#xFF1A;</p>
<pre><code class="lang-Go">ages := <span class="hljs-built_in">make</span>(<span class="hljs-keyword">map</span>[<span class="hljs-keyword">string</span>]<span class="hljs-keyword">int</span>) <span class="hljs-comment">// mapping from strings to ints</span>
</code></pre>
<p>&#x6211;&#x4EEC;&#x4E5F;&#x53EF;&#x4EE5;&#x7528;map&#x5B57;&#x9762;&#x503C;&#x7684;&#x8BED;&#x6CD5;&#x521B;&#x5EFA;map&#xFF0C;&#x540C;&#x65F6;&#x8FD8;&#x53EF;&#x4EE5;&#x6307;&#x5B9A;&#x4E00;&#x4E9B;&#x6700;&#x521D;&#x7684;key/value&#xFF1A;</p>
<pre><code class="lang-Go">ages := <span class="hljs-keyword">map</span>[<span class="hljs-keyword">string</span>]<span class="hljs-keyword">int</span>{
    <span class="hljs-string">&quot;alice&quot;</span>:   <span class="hljs-number">31</span>,
    <span class="hljs-string">&quot;charlie&quot;</span>: <span class="hljs-number">34</span>,
}
</code></pre>
<p>&#x8FD9;&#x76F8;&#x5F53;&#x4E8E;</p>
<pre><code class="lang-Go">ages := <span class="hljs-built_in">make</span>(<span class="hljs-keyword">map</span>[<span class="hljs-keyword">string</span>]<span class="hljs-keyword">int</span>)
ages[<span class="hljs-string">&quot;alice&quot;</span>] = <span class="hljs-number">31</span>
ages[<span class="hljs-string">&quot;charlie&quot;</span>] = <span class="hljs-number">34</span>
</code></pre>
<p>&#x56E0;&#x6B64;&#xFF0C;&#x53E6;&#x4E00;&#x79CD;&#x521B;&#x5EFA;&#x7A7A;&#x7684;map&#x7684;&#x8868;&#x8FBE;&#x5F0F;&#x662F;<code>map[string]int{}</code>&#x3002;</p>
<p>Map&#x4E2D;&#x7684;&#x5143;&#x7D20;&#x901A;&#x8FC7;key&#x5BF9;&#x5E94;&#x7684;&#x4E0B;&#x6807;&#x8BED;&#x6CD5;&#x8BBF;&#x95EE;&#xFF1A;</p>
<pre><code class="lang-Go">ages[<span class="hljs-string">&quot;alice&quot;</span>] = <span class="hljs-number">32</span>
fmt.Println(ages[<span class="hljs-string">&quot;alice&quot;</span>]) <span class="hljs-comment">// &quot;32&quot;</span>
</code></pre>
<p>&#x4F7F;&#x7528;&#x5185;&#x7F6E;&#x7684;delete&#x51FD;&#x6570;&#x53EF;&#x4EE5;&#x5220;&#x9664;&#x5143;&#x7D20;&#xFF1A;</p>
<pre><code class="lang-Go"><span class="hljs-built_in">delete</span>(ages, <span class="hljs-string">&quot;alice&quot;</span>) <span class="hljs-comment">// remove element ages[&quot;alice&quot;]</span>
</code></pre>
<p>&#x6240;&#x6709;&#x8FD9;&#x4E9B;&#x64CD;&#x4F5C;&#x662F;&#x5B89;&#x5168;&#x7684;&#xFF0C;&#x5373;&#x4F7F;&#x8FD9;&#x4E9B;&#x5143;&#x7D20;&#x4E0D;&#x5728;map&#x4E2D;&#x4E5F;&#x6CA1;&#x6709;&#x5173;&#x7CFB;&#xFF1B;&#x5982;&#x679C;&#x4E00;&#x4E2A;&#x67E5;&#x627E;&#x5931;&#x8D25;&#x5C06;&#x8FD4;&#x56DE;value&#x7C7B;&#x578B;&#x5BF9;&#x5E94;&#x7684;&#x96F6;&#x503C;&#xFF0C;&#x4F8B;&#x5982;&#xFF0C;&#x5373;&#x4F7F;map&#x4E2D;&#x4E0D;&#x5B58;&#x5728;&#x201C;bob&#x201D;&#x4E0B;&#x9762;&#x7684;&#x4EE3;&#x7801;&#x4E5F;&#x53EF;&#x4EE5;&#x6B63;&#x5E38;&#x5DE5;&#x4F5C;&#xFF0C;&#x56E0;&#x4E3A;ages[&quot;bob&quot;]&#x5931;&#x8D25;&#x65F6;&#x5C06;&#x8FD4;&#x56DE;0&#x3002;</p>
<pre><code class="lang-Go">ages[<span class="hljs-string">&quot;bob&quot;</span>] = ages[<span class="hljs-string">&quot;bob&quot;</span>] + <span class="hljs-number">1</span> <span class="hljs-comment">// happy birthday!</span>
</code></pre>
<p>&#x800C;&#x4E14;<code>x += y</code>&#x548C;<code>x++</code>&#x7B49;&#x7B80;&#x77ED;&#x8D4B;&#x503C;&#x8BED;&#x6CD5;&#x4E5F;&#x53EF;&#x4EE5;&#x7528;&#x5728;map&#x4E0A;&#xFF0C;&#x6240;&#x4EE5;&#x4E0A;&#x9762;&#x7684;&#x4EE3;&#x7801;&#x53EF;&#x4EE5;&#x6539;&#x5199;&#x6210;</p>
<pre><code class="lang-Go">ages[<span class="hljs-string">&quot;bob&quot;</span>] += <span class="hljs-number">1</span>
</code></pre>
<p>&#x66F4;&#x7B80;&#x5355;&#x7684;&#x5199;&#x6CD5;</p>
<pre><code class="lang-Go">ages[<span class="hljs-string">&quot;bob&quot;</span>]++
</code></pre>
<p>&#x4F46;&#x662F;map&#x4E2D;&#x7684;&#x5143;&#x7D20;&#x5E76;&#x4E0D;&#x662F;&#x4E00;&#x4E2A;&#x53D8;&#x91CF;&#xFF0C;&#x56E0;&#x6B64;&#x6211;&#x4EEC;&#x4E0D;&#x80FD;&#x5BF9;map&#x7684;&#x5143;&#x7D20;&#x8FDB;&#x884C;&#x53D6;&#x5740;&#x64CD;&#x4F5C;&#xFF1A;</p>
<pre><code class="lang-Go">_ = &amp;ages[<span class="hljs-string">&quot;bob&quot;</span>] <span class="hljs-comment">// compile error: cannot take address of map element</span>
</code></pre>
<p>&#x7981;&#x6B62;&#x5BF9;map&#x5143;&#x7D20;&#x53D6;&#x5740;&#x7684;&#x539F;&#x56E0;&#x662F;map&#x53EF;&#x80FD;&#x968F;&#x7740;&#x5143;&#x7D20;&#x6570;&#x91CF;&#x7684;&#x589E;&#x957F;&#x800C;&#x91CD;&#x65B0;&#x5206;&#x914D;&#x66F4;&#x5927;&#x7684;&#x5185;&#x5B58;&#x7A7A;&#x95F4;&#xFF0C;&#x4ECE;&#x800C;&#x53EF;&#x80FD;&#x5BFC;&#x81F4;&#x4E4B;&#x524D;&#x7684;&#x5730;&#x5740;&#x65E0;&#x6548;&#x3002;</p>
<p>&#x8981;&#x60F3;&#x904D;&#x5386;map&#x4E2D;&#x5168;&#x90E8;&#x7684;key/value&#x5BF9;&#x7684;&#x8BDD;&#xFF0C;&#x53EF;&#x4EE5;&#x4F7F;&#x7528;range&#x98CE;&#x683C;&#x7684;for&#x5FAA;&#x73AF;&#x5B9E;&#x73B0;&#xFF0C;&#x548C;&#x4E4B;&#x524D;&#x7684;slice&#x904D;&#x5386;&#x8BED;&#x6CD5;&#x7C7B;&#x4F3C;&#x3002;&#x4E0B;&#x9762;&#x7684;&#x8FED;&#x4EE3;&#x8BED;&#x53E5;&#x5C06;&#x5728;&#x6BCF;&#x6B21;&#x8FED;&#x4EE3;&#x65F6;&#x8BBE;&#x7F6E;name&#x548C;age&#x53D8;&#x91CF;&#xFF0C;&#x5B83;&#x4EEC;&#x5BF9;&#x5E94;&#x4E0B;&#x4E00;&#x4E2A;&#x952E;/&#x503C;&#x5BF9;&#xFF1A;</p>
<pre><code class="lang-Go"><span class="hljs-keyword">for</span> name, age := <span class="hljs-keyword">range</span> ages {
    fmt.Printf(<span class="hljs-string">&quot;%s\t%d\n&quot;</span>, name, age)
}
</code></pre>
<p>Map&#x7684;&#x8FED;&#x4EE3;&#x987A;&#x5E8F;&#x662F;&#x4E0D;&#x786E;&#x5B9A;&#x7684;&#xFF0C;&#x5E76;&#x4E14;&#x4E0D;&#x540C;&#x7684;&#x54C8;&#x5E0C;&#x51FD;&#x6570;&#x5B9E;&#x73B0;&#x53EF;&#x80FD;&#x5BFC;&#x81F4;&#x4E0D;&#x540C;&#x7684;&#x904D;&#x5386;&#x987A;&#x5E8F;&#x3002;&#x5728;&#x5B9E;&#x8DF5;&#x4E2D;&#xFF0C;&#x904D;&#x5386;&#x7684;&#x987A;&#x5E8F;&#x662F;&#x968F;&#x673A;&#x7684;&#xFF0C;&#x6BCF;&#x4E00;&#x6B21;&#x904D;&#x5386;&#x7684;&#x987A;&#x5E8F;&#x90FD;&#x4E0D;&#x76F8;&#x540C;&#x3002;&#x8FD9;&#x662F;&#x6545;&#x610F;&#x7684;&#xFF0C;&#x6BCF;&#x6B21;&#x90FD;&#x4F7F;&#x7528;&#x968F;&#x673A;&#x7684;&#x904D;&#x5386;&#x987A;&#x5E8F;&#x53EF;&#x4EE5;&#x5F3A;&#x5236;&#x8981;&#x6C42;&#x7A0B;&#x5E8F;&#x4E0D;&#x4F1A;&#x4F9D;&#x8D56;&#x5177;&#x4F53;&#x7684;&#x54C8;&#x5E0C;&#x51FD;&#x6570;&#x5B9E;&#x73B0;&#x3002;&#x5982;&#x679C;&#x8981;&#x6309;&#x987A;&#x5E8F;&#x904D;&#x5386;key/value&#x5BF9;&#xFF0C;&#x6211;&#x4EEC;&#x5FC5;&#x987B;&#x663E;&#x5F0F;&#x5730;&#x5BF9;key&#x8FDB;&#x884C;&#x6392;&#x5E8F;&#xFF0C;&#x53EF;&#x4EE5;&#x4F7F;&#x7528;sort&#x5305;&#x7684;Strings&#x51FD;&#x6570;&#x5BF9;&#x5B57;&#x7B26;&#x4E32;slice&#x8FDB;&#x884C;&#x6392;&#x5E8F;&#x3002;&#x4E0B;&#x9762;&#x662F;&#x5E38;&#x89C1;&#x7684;&#x5904;&#x7406;&#x65B9;&#x5F0F;&#xFF1A;</p>
<pre><code class="lang-Go"><span class="hljs-keyword">import</span> <span class="hljs-string">&quot;sort&quot;</span>

<span class="hljs-keyword">var</span> names []<span class="hljs-keyword">string</span>
<span class="hljs-keyword">for</span> name := <span class="hljs-keyword">range</span> ages {
    names = <span class="hljs-built_in">append</span>(names, name)
}
sort.Strings(names)
<span class="hljs-keyword">for</span> _, name := <span class="hljs-keyword">range</span> names {
    fmt.Printf(<span class="hljs-string">&quot;%s\t%d\n&quot;</span>, name, ages[name])
}
</code></pre>
<p>&#x56E0;&#x4E3A;&#x6211;&#x4EEC;&#x4E00;&#x5F00;&#x59CB;&#x5C31;&#x77E5;&#x9053;names&#x7684;&#x6700;&#x7EC8;&#x5927;&#x5C0F;&#xFF0C;&#x56E0;&#x6B64;&#x7ED9;slice&#x5206;&#x914D;&#x4E00;&#x4E2A;&#x5408;&#x9002;&#x7684;&#x5927;&#x5C0F;&#x5C06;&#x4F1A;&#x66F4;&#x6709;&#x6548;&#x3002;&#x4E0B;&#x9762;&#x7684;&#x4EE3;&#x7801;&#x521B;&#x5EFA;&#x4E86;&#x4E00;&#x4E2A;&#x7A7A;&#x7684;slice&#xFF0C;&#x4F46;&#x662F;slice&#x7684;&#x5BB9;&#x91CF;&#x521A;&#x597D;&#x53EF;&#x4EE5;&#x653E;&#x4E0B;map&#x4E2D;&#x5168;&#x90E8;&#x7684;key&#xFF1A;</p>
<pre><code class="lang-Go">names := <span class="hljs-built_in">make</span>([]<span class="hljs-keyword">string</span>, <span class="hljs-number">0</span>, <span class="hljs-built_in">len</span>(ages))
</code></pre>
<p>&#x5728;&#x4E0A;&#x9762;&#x7684;&#x7B2C;&#x4E00;&#x4E2A;range&#x5FAA;&#x73AF;&#x4E2D;&#xFF0C;&#x6211;&#x4EEC;&#x53EA;&#x5173;&#x5FC3;map&#x4E2D;&#x7684;key&#xFF0C;&#x6240;&#x4EE5;&#x6211;&#x4EEC;&#x5FFD;&#x7565;&#x4E86;&#x7B2C;&#x4E8C;&#x4E2A;&#x5FAA;&#x73AF;&#x53D8;&#x91CF;&#x3002;&#x5728;&#x7B2C;&#x4E8C;&#x4E2A;&#x5FAA;&#x73AF;&#x4E2D;&#xFF0C;&#x6211;&#x4EEC;&#x53EA;&#x5173;&#x5FC3;names&#x4E2D;&#x7684;&#x540D;&#x5B57;&#xFF0C;&#x6240;&#x4EE5;&#x6211;&#x4EEC;&#x4F7F;&#x7528;&#x201C;_&#x201D;&#x7A7A;&#x767D;&#x6807;&#x8BC6;&#x7B26;&#x6765;&#x5FFD;&#x7565;&#x7B2C;&#x4E00;&#x4E2A;&#x5FAA;&#x73AF;&#x53D8;&#x91CF;&#xFF0C;&#x4E5F;&#x5C31;&#x662F;&#x8FED;&#x4EE3;slice&#x65F6;&#x7684;&#x7D22;&#x5F15;&#x3002;</p>
<p>map&#x7C7B;&#x578B;&#x7684;&#x96F6;&#x503C;&#x662F;nil&#xFF0C;&#x4E5F;&#x5C31;&#x662F;&#x6CA1;&#x6709;&#x5F15;&#x7528;&#x4EFB;&#x4F55;&#x54C8;&#x5E0C;&#x8868;&#x3002;</p>
<pre><code class="lang-Go"><span class="hljs-keyword">var</span> ages <span class="hljs-keyword">map</span>[<span class="hljs-keyword">string</span>]<span class="hljs-keyword">int</span>
fmt.Println(ages == <span class="hljs-literal">nil</span>)    <span class="hljs-comment">// &quot;true&quot;</span>
fmt.Println(<span class="hljs-built_in">len</span>(ages) == <span class="hljs-number">0</span>) <span class="hljs-comment">// &quot;true&quot;</span>
</code></pre>
<p>map&#x4E0A;&#x7684;&#x5927;&#x90E8;&#x5206;&#x64CD;&#x4F5C;&#xFF0C;&#x5305;&#x62EC;&#x67E5;&#x627E;&#x3001;&#x5220;&#x9664;&#x3001;len&#x548C;range&#x5FAA;&#x73AF;&#x90FD;&#x53EF;&#x4EE5;&#x5B89;&#x5168;&#x5DE5;&#x4F5C;&#x5728;nil&#x503C;&#x7684;map&#x4E0A;&#xFF0C;&#x5B83;&#x4EEC;&#x7684;&#x884C;&#x4E3A;&#x548C;&#x4E00;&#x4E2A;&#x7A7A;&#x7684;map&#x7C7B;&#x4F3C;&#x3002;&#x4F46;&#x662F;&#x5411;&#x4E00;&#x4E2A;nil&#x503C;&#x7684;map&#x5B58;&#x5165;&#x5143;&#x7D20;&#x5C06;&#x5BFC;&#x81F4;&#x4E00;&#x4E2A;panic&#x5F02;&#x5E38;&#xFF1A;</p>
<pre><code class="lang-Go">ages[<span class="hljs-string">&quot;carol&quot;</span>] = <span class="hljs-number">21</span> <span class="hljs-comment">// panic: assignment to entry in nil map</span>
</code></pre>
<p>&#x5728;&#x5411;map&#x5B58;&#x6570;&#x636E;&#x524D;&#x5FC5;&#x987B;&#x5148;&#x521B;&#x5EFA;map&#x3002;</p>
<p>&#x901A;&#x8FC7;key&#x4F5C;&#x4E3A;&#x7D22;&#x5F15;&#x4E0B;&#x6807;&#x6765;&#x8BBF;&#x95EE;map&#x5C06;&#x4EA7;&#x751F;&#x4E00;&#x4E2A;value&#x3002;&#x5982;&#x679C;key&#x5728;map&#x4E2D;&#x662F;&#x5B58;&#x5728;&#x7684;&#xFF0C;&#x90A3;&#x4E48;&#x5C06;&#x5F97;&#x5230;&#x4E0E;key&#x5BF9;&#x5E94;&#x7684;value&#xFF1B;&#x5982;&#x679C;key&#x4E0D;&#x5B58;&#x5728;&#xFF0C;&#x90A3;&#x4E48;&#x5C06;&#x5F97;&#x5230;value&#x5BF9;&#x5E94;&#x7C7B;&#x578B;&#x7684;&#x96F6;&#x503C;&#xFF0C;&#x6B63;&#x5982;&#x6211;&#x4EEC;&#x524D;&#x9762;&#x770B;&#x5230;&#x7684;ages[&quot;bob&quot;]&#x90A3;&#x6837;&#x3002;&#x8FD9;&#x4E2A;&#x89C4;&#x5219;&#x5F88;&#x5B9E;&#x7528;&#xFF0C;&#x4F46;&#x662F;&#x6709;&#x65F6;&#x5019;&#x53EF;&#x80FD;&#x9700;&#x8981;&#x77E5;&#x9053;&#x5BF9;&#x5E94;&#x7684;&#x5143;&#x7D20;&#x662F;&#x5426;&#x771F;&#x7684;&#x662F;&#x5728;map&#x4E4B;&#x4E2D;&#x3002;&#x4F8B;&#x5982;&#xFF0C;&#x5982;&#x679C;&#x5143;&#x7D20;&#x7C7B;&#x578B;&#x662F;&#x4E00;&#x4E2A;&#x6570;&#x5B57;&#xFF0C;&#x4F60;&#x53EF;&#x80FD;&#x9700;&#x8981;&#x533A;&#x5206;&#x4E00;&#x4E2A;&#x5DF2;&#x7ECF;&#x5B58;&#x5728;&#x7684;0&#xFF0C;&#x548C;&#x4E0D;&#x5B58;&#x5728;&#x800C;&#x8FD4;&#x56DE;&#x96F6;&#x503C;&#x7684;0&#xFF0C;&#x53EF;&#x4EE5;&#x50CF;&#x4E0B;&#x9762;&#x8FD9;&#x6837;&#x6D4B;&#x8BD5;&#xFF1A;</p>
<pre><code class="lang-Go">age, ok := ages[<span class="hljs-string">&quot;bob&quot;</span>]
<span class="hljs-keyword">if</span> !ok { <span class="hljs-comment">/* &quot;bob&quot; is not a key in this map; age == 0. */</span> }
</code></pre>
<p>&#x4F60;&#x4F1A;&#x7ECF;&#x5E38;&#x770B;&#x5230;&#x5C06;&#x8FD9;&#x4E24;&#x4E2A;&#x7ED3;&#x5408;&#x8D77;&#x6765;&#x4F7F;&#x7528;&#xFF0C;&#x50CF;&#x8FD9;&#x6837;&#xFF1A;</p>
<pre><code class="lang-Go"><span class="hljs-keyword">if</span> age, ok := ages[<span class="hljs-string">&quot;bob&quot;</span>]; !ok { <span class="hljs-comment">/* ... */</span> }
</code></pre>
<p>&#x5728;&#x8FD9;&#x79CD;&#x573A;&#x666F;&#x4E0B;&#xFF0C;map&#x7684;&#x4E0B;&#x6807;&#x8BED;&#x6CD5;&#x5C06;&#x4EA7;&#x751F;&#x4E24;&#x4E2A;&#x503C;&#xFF1B;&#x7B2C;&#x4E8C;&#x4E2A;&#x662F;&#x4E00;&#x4E2A;&#x5E03;&#x5C14;&#x503C;&#xFF0C;&#x7528;&#x4E8E;&#x62A5;&#x544A;&#x5143;&#x7D20;&#x662F;&#x5426;&#x771F;&#x7684;&#x5B58;&#x5728;&#x3002;&#x5E03;&#x5C14;&#x53D8;&#x91CF;&#x4E00;&#x822C;&#x547D;&#x540D;&#x4E3A;ok&#xFF0C;&#x7279;&#x522B;&#x9002;&#x5408;&#x9A6C;&#x4E0A;&#x7528;&#x4E8E;if&#x6761;&#x4EF6;&#x5224;&#x65AD;&#x90E8;&#x5206;&#x3002;</p>
<p>&#x548C;slice&#x4E00;&#x6837;&#xFF0C;map&#x4E4B;&#x95F4;&#x4E5F;&#x4E0D;&#x80FD;&#x8FDB;&#x884C;&#x76F8;&#x7B49;&#x6BD4;&#x8F83;&#xFF1B;&#x552F;&#x4E00;&#x7684;&#x4F8B;&#x5916;&#x662F;&#x548C;nil&#x8FDB;&#x884C;&#x6BD4;&#x8F83;&#x3002;&#x8981;&#x5224;&#x65AD;&#x4E24;&#x4E2A;map&#x662F;&#x5426;&#x5305;&#x542B;&#x76F8;&#x540C;&#x7684;key&#x548C;value&#xFF0C;&#x6211;&#x4EEC;&#x5FC5;&#x987B;&#x901A;&#x8FC7;&#x4E00;&#x4E2A;&#x5FAA;&#x73AF;&#x5B9E;&#x73B0;&#xFF1A;</p>
<pre><code class="lang-Go"><span class="hljs-keyword">func</span> equal(x, y <span class="hljs-keyword">map</span>[<span class="hljs-keyword">string</span>]<span class="hljs-keyword">int</span>) <span class="hljs-keyword">bool</span> {
    <span class="hljs-keyword">if</span> <span class="hljs-built_in">len</span>(x) != <span class="hljs-built_in">len</span>(y) {
        <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>
    }
    <span class="hljs-keyword">for</span> k, xv := <span class="hljs-keyword">range</span> x {
        <span class="hljs-keyword">if</span> yv, ok := y[k]; !ok || yv != xv {
            <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>
        }
    }
    <span class="hljs-keyword">return</span> <span class="hljs-literal">true</span>
}
</code></pre>
<p>&#x4ECE;&#x4F8B;&#x5B50;&#x4E2D;&#x53EF;&#x4EE5;&#x770B;&#x5230;&#x5982;&#x4F55;&#x7528;!ok&#x6765;&#x533A;&#x5206;&#x5143;&#x7D20;&#x4E0D;&#x5B58;&#x5728;&#xFF0C;&#x4E0E;&#x5143;&#x7D20;&#x5B58;&#x5728;&#x4F46;&#x4E3A;0&#x7684;&#x3002;&#x6211;&#x4EEC;&#x4E0D;&#x80FD;&#x7B80;&#x5355;&#x5730;&#x7528;xv != y[k]&#x5224;&#x65AD;&#xFF0C;&#x90A3;&#x6837;&#x4F1A;&#x5BFC;&#x81F4;&#x5728;&#x5224;&#x65AD;&#x4E0B;&#x9762;&#x4E24;&#x4E2A;map&#x65F6;&#x4EA7;&#x751F;&#x9519;&#x8BEF;&#x7684;&#x7ED3;&#x679C;&#xFF1A;</p>
<pre><code class="lang-Go"><span class="hljs-comment">// True if equal is written incorrectly.</span>
equal(<span class="hljs-keyword">map</span>[<span class="hljs-keyword">string</span>]<span class="hljs-keyword">int</span>{<span class="hljs-string">&quot;A&quot;</span>: <span class="hljs-number">0</span>}, <span class="hljs-keyword">map</span>[<span class="hljs-keyword">string</span>]<span class="hljs-keyword">int</span>{<span class="hljs-string">&quot;B&quot;</span>: <span class="hljs-number">42</span>})
</code></pre>
<p>Go&#x8BED;&#x8A00;&#x4E2D;&#x5E76;&#x6CA1;&#x6709;&#x63D0;&#x4F9B;&#x4E00;&#x4E2A;set&#x7C7B;&#x578B;&#xFF0C;&#x4F46;&#x662F;map&#x4E2D;&#x7684;key&#x4E5F;&#x662F;&#x4E0D;&#x76F8;&#x540C;&#x7684;&#xFF0C;&#x53EF;&#x4EE5;&#x7528;map&#x5B9E;&#x73B0;&#x7C7B;&#x4F3C;set&#x7684;&#x529F;&#x80FD;&#x3002;&#x4E3A;&#x4E86;&#x8BF4;&#x660E;&#x8FD9;&#x4E00;&#x70B9;&#xFF0C;&#x4E0B;&#x9762;&#x7684;dedup&#x7A0B;&#x5E8F;&#x8BFB;&#x53D6;&#x591A;&#x884C;&#x8F93;&#x5165;&#xFF0C;&#x4F46;&#x662F;&#x53EA;&#x6253;&#x5370;&#x7B2C;&#x4E00;&#x6B21;&#x51FA;&#x73B0;&#x7684;&#x884C;&#x3002;&#xFF08;&#x5B83;&#x662F;1.3&#x8282;&#x4E2D;&#x51FA;&#x73B0;&#x7684;dup&#x7A0B;&#x5E8F;&#x7684;&#x53D8;&#x4F53;&#x3002;&#xFF09;dedup&#x7A0B;&#x5E8F;&#x901A;&#x8FC7;map&#x6765;&#x8868;&#x793A;&#x6240;&#x6709;&#x7684;&#x8F93;&#x5165;&#x884C;&#x6240;&#x5BF9;&#x5E94;&#x7684;set&#x96C6;&#x5408;&#xFF0C;&#x4EE5;&#x786E;&#x4FDD;&#x5DF2;&#x7ECF;&#x5728;&#x96C6;&#x5408;&#x5B58;&#x5728;&#x7684;&#x884C;&#x4E0D;&#x4F1A;&#x88AB;&#x91CD;&#x590D;&#x6253;&#x5370;&#x3002;</p>
<p><u><i>gopl.io/ch4/dedup</i></u></p>
<pre><code class="lang-Go"><span class="hljs-keyword">func</span> main() {
    seen := <span class="hljs-built_in">make</span>(<span class="hljs-keyword">map</span>[<span class="hljs-keyword">string</span>]<span class="hljs-keyword">bool</span>) <span class="hljs-comment">// a set of strings</span>
    input := bufio.NewScanner(os.Stdin)
    <span class="hljs-keyword">for</span> input.Scan() {
        line := input.Text()
        <span class="hljs-keyword">if</span> !seen[line] {
            seen[line] = <span class="hljs-literal">true</span>
            fmt.Println(line)
        }
    }

    <span class="hljs-keyword">if</span> err := input.Err(); err != <span class="hljs-literal">nil</span> {
        fmt.Fprintf(os.Stderr, <span class="hljs-string">&quot;dedup: %v\n&quot;</span>, err)
        os.Exit(<span class="hljs-number">1</span>)
    }
}
</code></pre>
<p>Go&#x7A0B;&#x5E8F;&#x5458;&#x5C06;&#x8FD9;&#x79CD;&#x5FFD;&#x7565;value&#x7684;map&#x5F53;&#x4F5C;&#x4E00;&#x4E2A;&#x5B57;&#x7B26;&#x4E32;&#x96C6;&#x5408;&#xFF0C;&#x5E76;&#x975E;&#x6240;&#x6709;<code>map[string]bool</code>&#x7C7B;&#x578B;value&#x90FD;&#x662F;&#x65E0;&#x5173;&#x7D27;&#x8981;&#x7684;&#xFF1B;&#x6709;&#x4E00;&#x4E9B;&#x5219;&#x53EF;&#x80FD;&#x4F1A;&#x540C;&#x65F6;&#x5305;&#x542B;true&#x548C;false&#x7684;&#x503C;&#x3002;</p>
<p>&#x6709;&#x65F6;&#x5019;&#x6211;&#x4EEC;&#x9700;&#x8981;&#x4E00;&#x4E2A;map&#x6216;set&#x7684;key&#x662F;slice&#x7C7B;&#x578B;&#xFF0C;&#x4F46;&#x662F;map&#x7684;key&#x5FC5;&#x987B;&#x662F;&#x53EF;&#x6BD4;&#x8F83;&#x7684;&#x7C7B;&#x578B;&#xFF0C;&#x4F46;&#x662F;slice&#x5E76;&#x4E0D;&#x6EE1;&#x8DB3;&#x8FD9;&#x4E2A;&#x6761;&#x4EF6;&#x3002;&#x4E0D;&#x8FC7;&#xFF0C;&#x6211;&#x4EEC;&#x53EF;&#x4EE5;&#x901A;&#x8FC7;&#x4E24;&#x4E2A;&#x6B65;&#x9AA4;&#x7ED5;&#x8FC7;&#x8FD9;&#x4E2A;&#x9650;&#x5236;&#x3002;&#x7B2C;&#x4E00;&#x6B65;&#xFF0C;&#x5B9A;&#x4E49;&#x4E00;&#x4E2A;&#x8F85;&#x52A9;&#x51FD;&#x6570;k&#xFF0C;&#x5C06;slice&#x8F6C;&#x4E3A;map&#x5BF9;&#x5E94;&#x7684;string&#x7C7B;&#x578B;&#x7684;key&#xFF0C;&#x786E;&#x4FDD;&#x53EA;&#x6709;x&#x548C;y&#x76F8;&#x7B49;&#x65F6;k(x) == k(y)&#x624D;&#x6210;&#x7ACB;&#x3002;&#x7136;&#x540E;&#x521B;&#x5EFA;&#x4E00;&#x4E2A;key&#x4E3A;string&#x7C7B;&#x578B;&#x7684;map&#xFF0C;&#x5728;&#x6BCF;&#x6B21;&#x5BF9;map&#x64CD;&#x4F5C;&#x65F6;&#x5148;&#x7528;k&#x8F85;&#x52A9;&#x51FD;&#x6570;&#x5C06;slice&#x8F6C;&#x5316;&#x4E3A;string&#x7C7B;&#x578B;&#x3002;</p>
<p>&#x4E0B;&#x9762;&#x7684;&#x4F8B;&#x5B50;&#x6F14;&#x793A;&#x4E86;&#x5982;&#x4F55;&#x4F7F;&#x7528;map&#x6765;&#x8BB0;&#x5F55;&#x63D0;&#x4EA4;&#x76F8;&#x540C;&#x7684;&#x5B57;&#x7B26;&#x4E32;&#x5217;&#x8868;&#x7684;&#x6B21;&#x6570;&#x3002;&#x5B83;&#x4F7F;&#x7528;&#x4E86;fmt.Sprintf&#x51FD;&#x6570;&#x5C06;&#x5B57;&#x7B26;&#x4E32;&#x5217;&#x8868;&#x8F6C;&#x6362;&#x4E3A;&#x4E00;&#x4E2A;&#x5B57;&#x7B26;&#x4E32;&#x4EE5;&#x7528;&#x4E8E;map&#x7684;key&#xFF0C;&#x901A;&#x8FC7;%q&#x53C2;&#x6570;&#x5FE0;&#x5B9E;&#x5730;&#x8BB0;&#x5F55;&#x6BCF;&#x4E2A;&#x5B57;&#x7B26;&#x4E32;&#x5143;&#x7D20;&#x7684;&#x4FE1;&#x606F;&#xFF1A;</p>
<pre><code class="lang-Go"><span class="hljs-keyword">var</span> m = <span class="hljs-built_in">make</span>(<span class="hljs-keyword">map</span>[<span class="hljs-keyword">string</span>]<span class="hljs-keyword">int</span>)

<span class="hljs-keyword">func</span> k(list []<span class="hljs-keyword">string</span>) <span class="hljs-keyword">string</span> { <span class="hljs-keyword">return</span> fmt.Sprintf(<span class="hljs-string">&quot;%q&quot;</span>, list) }

<span class="hljs-keyword">func</span> Add(list []<span class="hljs-keyword">string</span>)       { m[k(list)]++ }
<span class="hljs-keyword">func</span> Count(list []<span class="hljs-keyword">string</span>) <span class="hljs-keyword">int</span> { <span class="hljs-keyword">return</span> m[k(list)] }
</code></pre>
<p>&#x4F7F;&#x7528;&#x540C;&#x6837;&#x7684;&#x6280;&#x672F;&#x53EF;&#x4EE5;&#x5904;&#x7406;&#x4EFB;&#x4F55;&#x4E0D;&#x53EF;&#x6BD4;&#x8F83;&#x7684;key&#x7C7B;&#x578B;&#xFF0C;&#x800C;&#x4E0D;&#x4EC5;&#x4EC5;&#x662F;slice&#x7C7B;&#x578B;&#x3002;&#x8FD9;&#x79CD;&#x6280;&#x672F;&#x5BF9;&#x4E8E;&#x60F3;&#x4F7F;&#x7528;&#x81EA;&#x5B9A;&#x4E49;key&#x6BD4;&#x8F83;&#x51FD;&#x6570;&#x7684;&#x65F6;&#x5019;&#x4E5F;&#x5F88;&#x6709;&#x7528;&#xFF0C;&#x4F8B;&#x5982;&#x5728;&#x6BD4;&#x8F83;&#x5B57;&#x7B26;&#x4E32;&#x7684;&#x65F6;&#x5019;&#x5FFD;&#x7565;&#x5927;&#x5C0F;&#x5199;&#x3002;&#x540C;&#x65F6;&#xFF0C;&#x8F85;&#x52A9;&#x51FD;&#x6570;k(x)&#x4E5F;&#x4E0D;&#x4E00;&#x5B9A;&#x662F;&#x5B57;&#x7B26;&#x4E32;&#x7C7B;&#x578B;&#xFF0C;&#x5B83;&#x53EF;&#x4EE5;&#x8FD4;&#x56DE;&#x4EFB;&#x4F55;&#x53EF;&#x6BD4;&#x8F83;&#x7684;&#x7C7B;&#x578B;&#xFF0C;&#x4F8B;&#x5982;&#x6574;&#x6570;&#x3001;&#x6570;&#x7EC4;&#x6216;&#x7ED3;&#x6784;&#x4F53;&#x7B49;&#x3002;</p>
<p>&#x8FD9;&#x662F;map&#x7684;&#x53E6;&#x4E00;&#x4E2A;&#x4F8B;&#x5B50;&#xFF0C;&#x4E0B;&#x9762;&#x7684;&#x7A0B;&#x5E8F;&#x7528;&#x4E8E;&#x7EDF;&#x8BA1;&#x8F93;&#x5165;&#x4E2D;&#x6BCF;&#x4E2A;Unicode&#x7801;&#x70B9;&#x51FA;&#x73B0;&#x7684;&#x6B21;&#x6570;&#x3002;&#x867D;&#x7136;Unicode&#x5168;&#x90E8;&#x7801;&#x70B9;&#x7684;&#x6570;&#x91CF;&#x5DE8;&#x5927;&#xFF0C;&#x4F46;&#x662F;&#x51FA;&#x73B0;&#x5728;&#x7279;&#x5B9A;&#x6587;&#x6863;&#x4E2D;&#x7684;&#x5B57;&#x7B26;&#x79CD;&#x7C7B;&#x5E76;&#x6CA1;&#x6709;&#x591A;&#x5C11;&#xFF0C;&#x4F7F;&#x7528;map&#x53EF;&#x4EE5;&#x7528;&#x6BD4;&#x8F83;&#x81EA;&#x7136;&#x7684;&#x65B9;&#x5F0F;&#x6765;&#x8DDF;&#x8E2A;&#x90A3;&#x4E9B;&#x51FA;&#x73B0;&#x8FC7;&#x7684;&#x5B57;&#x7B26;&#x7684;&#x6B21;&#x6570;&#x3002;</p>
<p><u><i>gopl.io/ch4/charcount</i></u></p>
<pre><code class="lang-Go"><span class="hljs-comment">// Charcount computes counts of Unicode characters.</span>
<span class="hljs-keyword">package</span> main

<span class="hljs-keyword">import</span> (
    <span class="hljs-string">&quot;bufio&quot;</span>
    <span class="hljs-string">&quot;fmt&quot;</span>
    <span class="hljs-string">&quot;io&quot;</span>
    <span class="hljs-string">&quot;os&quot;</span>
    <span class="hljs-string">&quot;unicode&quot;</span>
    <span class="hljs-string">&quot;unicode/utf8&quot;</span>
)

<span class="hljs-keyword">func</span> main() {
    counts := <span class="hljs-built_in">make</span>(<span class="hljs-keyword">map</span>[<span class="hljs-keyword">rune</span>]<span class="hljs-keyword">int</span>)    <span class="hljs-comment">// counts of Unicode characters</span>
    <span class="hljs-keyword">var</span> utflen [utf8.UTFMax + <span class="hljs-number">1</span>]<span class="hljs-keyword">int</span> <span class="hljs-comment">// count of lengths of UTF-8 encodings</span>
    invalid := <span class="hljs-number">0</span>                    <span class="hljs-comment">// count of invalid UTF-8 characters</span>

    in := bufio.NewReader(os.Stdin)
    <span class="hljs-keyword">for</span> {
        r, n, err := in.ReadRune() <span class="hljs-comment">// returns rune, nbytes, error</span>
        <span class="hljs-keyword">if</span> err == io.EOF {
            <span class="hljs-keyword">break</span>
        }
        <span class="hljs-keyword">if</span> err != <span class="hljs-literal">nil</span> {
            fmt.Fprintf(os.Stderr, <span class="hljs-string">&quot;charcount: %v\n&quot;</span>, err)
            os.Exit(<span class="hljs-number">1</span>)
        }
        <span class="hljs-keyword">if</span> r == unicode.ReplacementChar &amp;&amp; n == <span class="hljs-number">1</span> {
            invalid++
            <span class="hljs-keyword">continue</span>
        }
        counts[r]++
        utflen[n]++
    }
    fmt.Printf(<span class="hljs-string">&quot;rune\tcount\n&quot;</span>)
    <span class="hljs-keyword">for</span> c, n := <span class="hljs-keyword">range</span> counts {
        fmt.Printf(<span class="hljs-string">&quot;%q\t%d\n&quot;</span>, c, n)
    }
    fmt.Print(<span class="hljs-string">&quot;\nlen\tcount\n&quot;</span>)
    <span class="hljs-keyword">for</span> i, n := <span class="hljs-keyword">range</span> utflen {
        <span class="hljs-keyword">if</span> i &gt; <span class="hljs-number">0</span> {
            fmt.Printf(<span class="hljs-string">&quot;%d\t%d\n&quot;</span>, i, n)
        }
    }
    <span class="hljs-keyword">if</span> invalid &gt; <span class="hljs-number">0</span> {
        fmt.Printf(<span class="hljs-string">&quot;\n%d invalid UTF-8 characters\n&quot;</span>, invalid)
    }
}
</code></pre>
<p>ReadRune&#x65B9;&#x6CD5;&#x6267;&#x884C;UTF-8&#x89E3;&#x7801;&#x5E76;&#x8FD4;&#x56DE;&#x4E09;&#x4E2A;&#x503C;&#xFF1A;&#x89E3;&#x7801;&#x7684;rune&#x5B57;&#x7B26;&#x7684;&#x503C;&#xFF0C;&#x5B57;&#x7B26;UTF-8&#x7F16;&#x7801;&#x540E;&#x7684;&#x957F;&#x5EA6;&#xFF0C;&#x548C;&#x4E00;&#x4E2A;&#x9519;&#x8BEF;&#x503C;&#x3002;&#x6211;&#x4EEC;&#x53EF;&#x9884;&#x671F;&#x7684;&#x9519;&#x8BEF;&#x503C;&#x53EA;&#x6709;&#x5BF9;&#x5E94;&#x6587;&#x4EF6;&#x7ED3;&#x5C3E;&#x7684;io.EOF&#x3002;&#x5982;&#x679C;&#x8F93;&#x5165;&#x7684;&#x662F;&#x65E0;&#x6548;&#x7684;UTF-8&#x7F16;&#x7801;&#x7684;&#x5B57;&#x7B26;&#xFF0C;&#x8FD4;&#x56DE;&#x7684;&#x5C06;&#x662F;unicode.ReplacementChar&#x8868;&#x793A;&#x65E0;&#x6548;&#x5B57;&#x7B26;&#xFF0C;&#x5E76;&#x4E14;&#x7F16;&#x7801;&#x957F;&#x5EA6;&#x662F;1&#x3002;</p>
<p>charcount&#x7A0B;&#x5E8F;&#x540C;&#x65F6;&#x6253;&#x5370;&#x4E0D;&#x540C;UTF-8&#x7F16;&#x7801;&#x957F;&#x5EA6;&#x7684;&#x5B57;&#x7B26;&#x6570;&#x76EE;&#x3002;&#x5BF9;&#x6B64;&#xFF0C;map&#x5E76;&#x4E0D;&#x662F;&#x4E00;&#x4E2A;&#x5408;&#x9002;&#x7684;&#x6570;&#x636E;&#x7ED3;&#x6784;&#xFF1B;&#x56E0;&#x4E3A;UTF-8&#x7F16;&#x7801;&#x7684;&#x957F;&#x5EA6;&#x603B;&#x662F;&#x4ECE;1&#x5230;utf8.UTFMax&#xFF08;&#x6700;&#x5927;&#x662F;4&#x4E2A;&#x5B57;&#x8282;&#xFF09;&#xFF0C;&#x4F7F;&#x7528;&#x6570;&#x7EC4;&#x5C06;&#x66F4;&#x6709;&#x6548;&#x3002;</p>
<p>&#x4F5C;&#x4E3A;&#x4E00;&#x4E2A;&#x5B9E;&#x9A8C;&#xFF0C;&#x6211;&#x4EEC;&#x7528;charcount&#x7A0B;&#x5E8F;&#x5BF9;&#x82F1;&#x6587;&#x7248;&#x539F;&#x7A3F;&#x7684;&#x5B57;&#x7B26;&#x8FDB;&#x884C;&#x4E86;&#x7EDF;&#x8BA1;&#x3002;&#x867D;&#x7136;&#x5927;&#x90E8;&#x5206;&#x662F;&#x82F1;&#x8BED;&#xFF0C;&#x4F46;&#x662F;&#x4E5F;&#x6709;&#x4E00;&#x4E9B;&#x975E;ASCII&#x5B57;&#x7B26;&#x3002;&#x4E0B;&#x9762;&#x662F;&#x6392;&#x540D;&#x524D;10&#x7684;&#x975E;ASCII&#x5B57;&#x7B26;&#xFF1A;</p>
<p><img src="../images/ch4-xx-01.png" alt=""></p>
<p>&#x4E0B;&#x9762;&#x662F;&#x4E0D;&#x540C;UTF-8&#x7F16;&#x7801;&#x957F;&#x5EA6;&#x7684;&#x5B57;&#x7B26;&#x7684;&#x6570;&#x76EE;&#xFF1A;</p>
<pre><code>len count
1   765391
2   60
3   70
4   0
</code></pre><p>Map&#x7684;value&#x7C7B;&#x578B;&#x4E5F;&#x53EF;&#x4EE5;&#x662F;&#x4E00;&#x4E2A;&#x805A;&#x5408;&#x7C7B;&#x578B;&#xFF0C;&#x6BD4;&#x5982;&#x662F;&#x4E00;&#x4E2A;map&#x6216;slice&#x3002;&#x5728;&#x4E0B;&#x9762;&#x7684;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;&#x56FE;graph&#x7684;key&#x7C7B;&#x578B;&#x662F;&#x4E00;&#x4E2A;&#x5B57;&#x7B26;&#x4E32;&#xFF0C;value&#x7C7B;&#x578B;map[string]bool&#x4EE3;&#x8868;&#x4E00;&#x4E2A;&#x5B57;&#x7B26;&#x4E32;&#x96C6;&#x5408;&#x3002;&#x4ECE;&#x6982;&#x5FF5;&#x4E0A;&#x8BB2;&#xFF0C;graph&#x5C06;&#x4E00;&#x4E2A;&#x5B57;&#x7B26;&#x4E32;&#x7C7B;&#x578B;&#x7684;key&#x6620;&#x5C04;&#x5230;&#x4E00;&#x7EC4;&#x76F8;&#x5173;&#x7684;&#x5B57;&#x7B26;&#x4E32;&#x96C6;&#x5408;&#xFF0C;&#x5B83;&#x4EEC;&#x6307;&#x5411;&#x65B0;&#x7684;graph&#x7684;key&#x3002;</p>
<p><u><i>gopl.io/ch4/graph</i></u></p>
<pre><code class="lang-Go"><span class="hljs-keyword">var</span> graph = <span class="hljs-built_in">make</span>(<span class="hljs-keyword">map</span>[<span class="hljs-keyword">string</span>]<span class="hljs-keyword">map</span>[<span class="hljs-keyword">string</span>]<span class="hljs-keyword">bool</span>)

<span class="hljs-keyword">func</span> addEdge(from, to <span class="hljs-keyword">string</span>) {
    edges := graph[from]
    <span class="hljs-keyword">if</span> edges == <span class="hljs-literal">nil</span> {
        edges = <span class="hljs-built_in">make</span>(<span class="hljs-keyword">map</span>[<span class="hljs-keyword">string</span>]<span class="hljs-keyword">bool</span>)
        graph[from] = edges
    }
    edges[to] = <span class="hljs-literal">true</span>
}

<span class="hljs-keyword">func</span> hasEdge(from, to <span class="hljs-keyword">string</span>) <span class="hljs-keyword">bool</span> {
    <span class="hljs-keyword">return</span> graph[from][to]
}
</code></pre>
<p>&#x5176;&#x4E2D;addEdge&#x51FD;&#x6570;&#x60F0;&#x6027;&#x521D;&#x59CB;&#x5316;map&#x662F;&#x4E00;&#x4E2A;&#x60EF;&#x7528;&#x65B9;&#x5F0F;&#xFF0C;&#x4E5F;&#x5C31;&#x662F;&#x8BF4;&#x5728;&#x6BCF;&#x4E2A;&#x503C;&#x9996;&#x6B21;&#x4F5C;&#x4E3A;key&#x65F6;&#x624D;&#x521D;&#x59CB;&#x5316;&#x3002;addEdge&#x51FD;&#x6570;&#x663E;&#x793A;&#x4E86;&#x5982;&#x4F55;&#x8BA9;map&#x7684;&#x96F6;&#x503C;&#x4E5F;&#x80FD;&#x6B63;&#x5E38;&#x5DE5;&#x4F5C;&#xFF1B;&#x5373;&#x4F7F;from&#x5230;to&#x7684;&#x8FB9;&#x4E0D;&#x5B58;&#x5728;&#xFF0C;graph[from][to]&#x4F9D;&#x7136;&#x53EF;&#x4EE5;&#x8FD4;&#x56DE;&#x4E00;&#x4E2A;&#x6709;&#x610F;&#x4E49;&#x7684;&#x7ED3;&#x679C;&#x3002;</p>
<p><strong>&#x7EC3;&#x4E60; 4.8&#xFF1A;</strong> &#x4FEE;&#x6539;charcount&#x7A0B;&#x5E8F;&#xFF0C;&#x4F7F;&#x7528;unicode.IsLetter&#x7B49;&#x76F8;&#x5173;&#x7684;&#x51FD;&#x6570;&#xFF0C;&#x7EDF;&#x8BA1;&#x5B57;&#x6BCD;&#x3001;&#x6570;&#x5B57;&#x7B49;Unicode&#x4E2D;&#x4E0D;&#x540C;&#x7684;&#x5B57;&#x7B26;&#x7C7B;&#x522B;&#x3002;</p>
<p><strong>&#x7EC3;&#x4E60; 4.9&#xFF1A;</strong> &#x7F16;&#x5199;&#x4E00;&#x4E2A;&#x7A0B;&#x5E8F;wordfreq&#x7A0B;&#x5E8F;&#xFF0C;&#x62A5;&#x544A;&#x8F93;&#x5165;&#x6587;&#x672C;&#x4E2D;&#x6BCF;&#x4E2A;&#x5355;&#x8BCD;&#x51FA;&#x73B0;&#x7684;&#x9891;&#x7387;&#x3002;&#x5728;&#x7B2C;&#x4E00;&#x6B21;&#x8C03;&#x7528;Scan&#x524D;&#x5148;&#x8C03;&#x7528;input.Split(bufio.ScanWords)&#x51FD;&#x6570;&#xFF0C;&#x8FD9;&#x6837;&#x53EF;&#x4EE5;&#x6309;&#x5355;&#x8BCD;&#x800C;&#x4E0D;&#x662F;&#x6309;&#x884C;&#x8F93;&#x5165;&#x3002;</p>

                                
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